Elastomers with improved processability

ABSTRACT

A process for improving the green strength of ethylene/α-olefin/diene polymers is described comprising (A) selecting an ethylene/α-olefin/diene polymer having a Mooney viscosity at 125 C up to about 80 and a percent gel (% gel) up to about 30 percent and (B) partially crosslinking the ethylene/α-olefin/diene polymer selected in step (A) to make a modified ethylene/α-olefin/diene polymer satisfying the equations MV≦100 and        W   ≤     (         MS   2     -     MS   1         MS   1       )                     
     wherein MV is the Mooney viscosity of the modified polymer, MS 1  is the melt strength in centiNewtons of the polymer selected in step (A) at 110 C, when formulated according to ASTM D3568#2, MS 2  is the melt strength in centiNewtons of the modified polymer produced by step (B) measured under the same conditions, and W is 0.3. Modified ethylene/α-olefin/diene polymers obtainable according to the above process or satisfying the equation:          MS   2     ≥       (       MV   X     +       %                 gel     Y       )        Z                     
     is also described in which MS 2 , MV and % gel of the modified polymer are defined as defined above, X is 50, Y is 20, and Z is 40. Further described is a process for making an article comprising an ethylene/α-olefin/diene polymer and intermediates for making the modified ethylene/α-olefin/diene polymers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/057,086 filed Aug. 27, 1997, the disclosure of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION:

1. Field of the Invention

This invention relates to processes for modifying elastomers, themodified elastomers made thereby, and processes for making products fromthe modified elastomers.

2. Background Information

The term “elastomer” was first defined in 1940 to mean syntheticthermosetting high polymers having properties similar to those ofvulcanized natural rubber, e.g. having the ability to be stretched to atleast twice their original length and to retract very rapidly toapproximately their original length when released. Representative ofthese “high polymers” were styrene-butadiene copolymer, polychloroprene,nitrite butyl rubber and ethylene-propylene polymers (aka EP and EPDMelastomers). The term “elastomer” was later extended to includeuncrosslinked thermoplastic polyolefins, i.e. TPOs.

ASTM D 1566 defines various physical properties of elastomers, and thetest methods for measuring these properties. U.S. Pat. No. 5,001,205provides an overview of known elastomers comprising ethylenecopolymerized with an α-olefin. As described therein, commerciallyviable elastomers have various minimum properties, e.g. a Mooneyviscosity no less than 10, a weight average molecular weight (M_(w)) noless than 110,000, a glass transition temperature below −20° C., and adegree of crystallinity no greater than 25%.

A dilemma faced in the production of commercially viable curedelastomers is that a high weight average molecular weight is generallydesired to improve physical properties such as tensile strength,toughness, compression set, etc., in the cured product, but the uncuredhigh molecular weight elastomers are more difficult to process thantheir lower molecular weight counterparts. In particular, the uncuredhigher molecular weight uncured elastomers are typically more difficultit is to isolate from solvents and residual monomer followingpolymerization of the elastomer. The uncured higher molecular weightelastomers are also typically more difficult to extrude at high rates,since they are generally prone to shear fracture at lower extrusionrates and require more power consumption by polymer processing equipmentsuch as batch mixers, continuous mixers, extruders, etc., and causeincreased wear on the parts of such equipment exposed to high shearstresses, such as expensive extruder components. These disadvantagesreduce production rates and/or increase the cost of production.

A conventional approach for resolving this dilemma is to make arelatively low molecular weight elastomer and then fully crosslink thefinal product to obtain the desired tensile strength, toughness,compression set, etc. A disadvantage of that approach is that the lowmolecular weight of the elastomer also generally corresponds to a low“green strength” (i.e., strength prior to crosslinking). Thatdisadvantage is particularly noticeable in applications such as coatingwire and cable, continuous extrusion of gaskets, etc., where low greenstrength results in sags or uneven polymer thickness. The presentinvention addresses these and other disadvantages.

SUMMARY OF THE INVENTION

This invention provides a process for improving the green strength ofethylene/α-olefin/diene polymers comprising:

(A) selecting an ethylene/α-olefin/diene polymer having a Mooney ML1+4viscosity, measured according to ASTM D 1646 at 125 C, up to about 80and a percent gel (% gel), measured according to ASTM D2765, ProcedureA, up to about 30 percent and

(B) partially crosslinking the ethylene/α-olefin/diene polymer selectedin step (A) to make a modified ethylene/α-olefin/diene polymersatisfying the following equations:$W \leq \left( \frac{{MS}_{2} - {MS}_{1}}{{MS}_{1}} \right)$

wherein MV is the Mooney viscosity of the modified polymer measured asdefined above, MS₁ is the melt strength in centiNewtons of the polymerselected in step (A) at 110 C, when formulated according to ASTMD3568#2, MS₂ is the melt strength in centiNewtons of the modifiedpolymer produced by step (B) measured under the same conditions, and Wis 0.3.

Another aspect of this invention is the modified ethylene/α-olefin/dienepolymers obtainable according to the above process, preferably when theysatisfy the equation:${MS}_{2} \geq {\left( {\frac{MV}{X} + \frac{\% \quad {gel}}{Y}} \right)Z}$

in which MS₂, MV and % gel of the modified polymer are measured asdefined above, X is 50, Y is 20, and Z is 40.

This invention also provides a process for making an article comprisingan ethylene/α-olefin/diene polymer comprising:

(A1) melt processing the modified polymer described above;

(B1) forming the product of step (A1) into a shape; and

(C1) curing the product of step (B1) to form an article comprising acrosslinked ethylene/α-olefin/diene polymer.

This invention also provides intermediates for making modifiedethylene/α-olefin/diene polymers according to the above processcomprising a polymer selected according to step (A) in combination withunreacted peroxide crosslinking agent in an amount appropriate to modifythe selected polymer according to that process under melt processingconditions.

This invention also provides another process for making an articlecomprising an ethylene/α-olefin/diene polymer comprising:

(A1) melt processing the above intermediate;

(B1) forming the product of step (A1) into a shape; and

(C1) curing the product of step (B1) to form an article comprising acrosslinked ethylene/α-olefin/diene polymer.

DETAILED DESCRIPTION OF THE INVENTION

Unless indicated to the contrary, all parts, percentages and ratios areby weight. The expression “up to” when used to specify a numerical rangeincludes any value less than or equal to the numerical value whichfollows this expression. The expression “wt %” means “weight percent”.

The term “crosslinking” as used herein refers to both tetrafunctional(H-type) long chain branching resulting from a covalent linkage betweentwo polymer molecule backbones and trifunctional (T-type) long chainbranching produced when a terminal group of a polymer molecule forms acovalent linkage with the backbone of another polymer molecule.

The term “gel” refers to a three-dimensional polymer network which isformed from covalently linked polymer chains. The amount of gel isexpressed in terms of weight-percent based on the total weight of thepolymer as determined by ASTM D2765, Procedure A.

The term “melt strength” refers to the strength of the elastomermeasured in centiNewtons at 110 C when it is formulated according toASTM D3568#2 according to a procedure described in more detail in theexamples below.

Unless specified otherwise, the term “Mooney viscosity” as used hereinmeans viscosity which is measured according to ASTM D1646, incorporatedherein by reference, using a sheer rheometer at 125 C and measuredaccording to ML 1+4.

The ethylene/α-olefin/diene polymers used to make rheology-modifiedpolymers according to this invention are polymers of ethylene (CH₂═CH₂)with at least one aliphatic C₃-C₂₀ α-olefin and at least one C₄-C₂₀diene. The diene ay be conjugated or nonconjugated.

Examples of the aliphatic C₃-C₂₀ α-olefins include propene, 1-butene,4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. The α-olefincan also contain a cyclic structure such as cyclohexane or cyclopentane,resulting in an α-olefin such as 3-cyclohexyl-1-propene(allylcyclohexane) and vinyl-cyclohexane.

Examples of nonconjugated dienes include aliphatic dienes such as1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2-methyl-1,5-hexadiene,1,6-heptadiene, 6-methyl-1,5-heptadiene, 1,6-octadiene, 1,7-octadiene,7-methyl-1,6-octadiene, 1,13-tetradecadiene, 1,19-eicosadiene, and thelike; cyclic dienes such as 1,4-cyclohexadiene,bicyclo[2.2.1]hept-2,5-diene, 5-ethylidene-2-norbornene (ENB),5-methylene-2-norbornene, 5-vinyl-2-norbornene,bicyclo[2.2.2]oct-2,5-diene, 4-vinylcyclohex-I-ene,bicyclo[2.2.2]oct2,6-diene,1,7,7-trimethylbicyclo-[2.2.1]hept-2,5-diene, dicyclopentadiene,ethyltetrahydroindene, 5-allylbicyclo[2.2.1]hept-2-ene,1,5-cyclooctadiene, and the like; aromatic dienes such as 1,4-diallylbenzene, 4-allyl-1H-indene; and trienes such as2,3-diisopropenylidiene-5-norbornene,2-ethylidene-3-isopropylidene5-norbornene, 2-propenyl-2,5-norbornadiene,1,3,7-octatriene, 1,4,9-decatriene, and the like; with5-ethylidene-2-norbornene a preferred nonconjugated diene.

Examples of conjugated dienes include butadiene, isoprene,2,3-dimethylbutadiene-1,3, 1,2-dimethylbutadiene-1,3,1,4-dimethylbutadiene-1,3, 1-ethylbutadiene-1,3, 2-phenylbutadiene-1,3,hexadiene-1,3, 4-methylpentadiene-1,3, 1,3-pentadiene (CH₃CH═CH—CH═CH₂;commonly called piperylene), 3-methyl1,3-pentadiene,2,4-dimethyl-1,3-pentadiene, 3-ethyl-1,3-pentadiene, and the like; with1,3-pentadiene a preferred conjugated diene.

Exemplary polymers includeethylene/propylene/-5-ethylidene-2-norbornene,ethylene/1-octene/5-ethylidene-2-norbornene,ethylene/-propylene/1,3-pentadiene, andethylene/1-octene/1,3-pentadiene. Exemplary tetrapolymers includeethylene/propylene/I-octene/diene (e.g. ENB) andethylene/propylene/mixed dienes, e.g.ethylene/propylene/5-ethylidene-2-norbornene/piperylene. In addition,the elastomers can include minor amounts, e.g. 0.05-0.5 percent byweight, of long chain branch enhancers, such as 2,5-norbomadiene (akabicyclo[2,2,1]hepta-2,5-diene), diallylbenzene, 1,7-octadiene(H₂C═CH(CH₂)₄CH═CH₂), and 1,9-decadiene (H₂C═CH(CH₂)₆CH═CH₂).

At a general minimum, the selected ethylene/α-olefin/diene polymers arederived from at least about 30, preferably at least about 40 and morepreferably at least about 50, weight percent ethylene; at least about15, preferably at least about 20 and more preferably at least about 25,weight percent of at least one α-olefin; and preferably at least about0.1, and more preferably at least about 0.5, weight percent of at leastone conjugated or nonconjugated diene. At a general maximum, theethylene/α-olefin/diene polymers selected for modification according tothis invention comprise not more than about 85, preferably not more thanabout 80 and more preferably not more than about 75, weight percentethylene; not more than about 70, preferably not more than about 60 andmore preferably not more than about 55, weight percent of at least oneα-olefin; and not more than about 20, preferably not more than about 15and more preferably not more than about 12, weight percent of at leastone of a conjugated or nonconjugated diene. All weight percentages arebased on weight of the elastomer which can be determined using anyconventional method.

The polydispersity (molecular weight distribution or Mw/Mn) of theselected polymer prior to modification generally ranges from about 1.5,preferably about 1.8, and especially about 2.0, to about 15, preferablyabout 10, and especially about 6.

Molecular Weight Distribution Determination

The whole interpolymer product samples and the individual interpolymercomponents are analyzed by gel permeation chromatography (GPC) on aWaters 150 C high temperature chromatographic unit equipped with threemixed porosity columns (Polymer Laboratories 10³, 10⁴, 10⁵, and 10⁶),operating at a system temperature of 140° C. The solvent is1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions ofthe samples are prepared for injection. The flow rate is 1.0milliliters/minute and the injection size is 100 microliters.

The molecular weight determination is deduced by using narrow molecularweight distribution polystyrene standards (from Polymer Laboratories) inconjunction with their elution volumes. The equivalent polyethylenemolecular weights are determined by using appropriate Mark-Houwinkcoefficients for polyethylene and polystyrene (as described by Williamsand Ward in Journal of Polymer Science, Polymer Letters, Vol. 6, (621)1968) to derive the following equation:

M_(polyethylene)=a*(M_(polystyrene))^(b).

In this equation, a=0.4316 and b=1.0. Weight average molecular weight,M_(w), and number average molecular weight, M_(n), is calculated in theusual manner according to the following formula:

M_(j)=(Σw_(i)(M_(i) ^(j)))^(j);

where w_(i) is the weight fraction of the molecules with molecularweight M_(i) eluting from the GPC column in fraction i and j=1 whencalculating M_(w) and j=−1 when calculating M_(n).

Generally the Mw of the interpolymer elastomers ranges from about10,000, preferably about 20,000, more preferably about 40,000, andespecially about 60,000 to about 1,000,000, preferably about 800,000,more preferably about 600,000, and especially about 500,000.

The polymers selected for modification cover a range of viscosities,depending upon their molecular weight. The Mooney viscosity for theselected polymers prior to modification according to this inventionpreferably ranges from a minimum of about 1, more preferably at leastabout 5, even more preferably at least about 10, and especially at leastabout 15, up to a maximum of about 80, more preferably up to about 65,even more preferably up to about 55, and especially up to about 45.

The density of the elastomers is measured according to ASTM D-792,incorporated herein by reference, and these densities range from aminimum of about 0.850 grams/cubic centimeter (g/cm³), preferably about0.853 g/cm³, and especially about 0.855 g/cm³, to a maximum of about0.895 g/cm³, preferably about 0.885 g/cm³, and especially about 0.875g/cm³.

The polymers selected for modification have a percent gel (% gel),measured according to ASTM D2765, Procedure A, up to about 30,preferably up to about 20, more preferably up to about 10 and even morepreferably up to about 5, percent.

The ethylene/α-olefin/diene polymer may be selected from any of thoseknown in the art and/or commercially available, including those that areheterogeneously branched, such as those produced using Ziegler-Nattatype catalysts, and those that are homogeneously branched. Examplesinclude ethylene/α-olefin/diene polymers available from DuPont DowElastomers L.L.C., such as NORDEL® and NORDEL® IP, for instance NORDEL®1040 and NORDEL® 1070 (each a 5 wt % ethylene, 44 wt % proplyene, and 3wt % 1,4-hexadiene (HD) derived EPDM), and those available from Exxonunder the name VISTALON™, for instance VISTALON™ 2504 (a 50 wt %ethylene, 45 wt % propylene and 5 wt % ethylidene norbornene (ENB)derived EPDM). The NORDEL® elastomers and how to make them are describedfor example in U.S. Pat. Nos. 2,933,480; 3,063,973; and 3,093,620, eachof which are incorporated herein by reference.

In a preferred embodiment, the selected ethylene/α-olefin/diene polymeris homogeneously branched. In one such preferred embodiment, theselected polymer is obtainable by (1) contacting in a reactor (a)ethylene, (b) at least one C₃-C₂₀ aliphatic α-olefin, (c) at least oneC₄-C₂₀ diene, (d) a catalyst, the catalyst comprising (i) a metallocenecomplex or single site catalyst and (ii) at least one activator, and (e)a diluent and (2) isolating the polymer product. These include, forexample, the NORDEL® IP elastomers from DuPont Dow Elastomers L.L.C.

The metallocene complexes (or single site catalysts) and methods fortheir preparation are disclosed in EP-A-416,815 and EP-A-514,828 as wellas in U.S. Pat. Nos. 5,470,993, 5,374,696, 5,231,106, 5,055,438,5,057,475, 5,091,352, 5,096,867, 5,064,802, 5,132,380, 5,153,157,5,183,867, 5,198,401, 5,272,236, 5,278,272, 5,321,106, 5,470,993, and5,486,632, each of which is incorporated herein by reference.Particularly preferred among the single site catalysts are the DowINSITE™ technology constrained geometry catalysts.

In EP-A-514,828, certain borane derivatives of the foregoing metallocenecomplex catalysts are disclosed and a method for their preparationtaught and claimed in U.S. Pat. No. 5,453,410 combinations of cationicmetallocene complex catalysts with an alumoxane were disclosed assuitable olefin polymerization catalysts.

For the teachings contained therein, the aforementioned U.S. Patents andpublished European Patent Applications are hereby incorporated byreference for their relevant disclosures.

Preferred catalyst compositions comprise:

a1) a metal complex corresponding to the formula: ZLMX_(p)X′_(q). thathas been or subsequently is rendered catalytically active by combinationwith an activating cocatalyst or by use of an activating technique,

wherein M is a metal of Group 4 of the Periodic Table of the Elementshaving an oxidation state of +2, +3 or +4, bound in an η⁵ bonding modeto L;

L is a cyclopentadienyl-, indenyl-, tetrahydroindenyl-, fluorenyl-,tetrahydrofluorenyl-, or octabydrofluorenyl-group covalently substitutedwith at least a divalent moiety, Z. and L further may be substitutedwith from 1 to 8 substituents independently selected from the groupconsisting of hydrocarbyl, halo, halohydrocarbyl, hydrocarbyloxy,dihydrocarbylamine, dihydrocarbylphosphino or silyl groups containing upto 20 nonhydrogen atoms;

Z is a divalent moiety bound to both L and M via cy-bonds, said Zcomprising boron, or a member of Group 14 of the Periodic Table of theElements, and optionally, also comprising nitrogen, phosphorus, sulfuror oxygen;

X is an anionic or dianionic ligand group having up to 60 atomsexclusive of the class of ligands that are cyclic, delocalized, π-boundligand groups;

X′ independently each occurrence is a neutral Lewis base ligatingcompounding, having up to 20 atoms;

p is 0, 1 or 2, and is two less than the formal oxidation state of M,with the proviso that when X is a dianionic ligand group, p is 1; and

q is 0, 1 or 2; said metal complex being rendered catalytically activeby combination with an activating cocatalyst or use of an activatingtechnique; or

a catalyst composition comprising a cationic complex a2) correspondingto the formula (ZLM*X*_(p*))*A⁻,

wherein: M* is a metal of Group 4 of the Periodic Table of the Elementshaving an oxidation state of +3 or +4, bound in an η⁵ bonding mode to L;

L is a cyclopentadienyl-, indenyl-, tetrahydroindenyl-, fluorenyl-,tetrahydrofluorenyl-, or octahydrofluorenyl-group covalently substitutedwith at least a divalent moiety, Z. and L further may be substitutedwith from 1 to 8 substituents independently selected from the groupconsisting of hydrocarbyl, halo, halohydrocarbyl, hydrocarbyloxy,dihydrocarbylamino, dihydrocarbylphosphino or silyl groups containing upto 20 nonhydrogen atoms;

Z is a divalent moiety bound to both L and M* via σ-bonds, said Zcomprising boron, or a member of Group 14 of the Periodic Table of theElements, and also optionally comprising nitrogen, phosphorus, sulfur oroxygen;

X* is an anionic ligand group having up to 60 atoms exclusive of theclass of ligands that are cyclic, delocalized, π-bound ligand groups;

p* is 0 or 1, and is three less than the formal oxidation state of M;and

A⁻ is an inert, noncoordinating anion.

Preferred X′ and X* groups when M is a metal of Group 4 of the PeriodicTable of Elements and has an oxidation state of +3 or +4 are alkyl,aryl, silyl, germyl, aryloxy, or alkoxy group having up to 20non-hydrogen atoms. Additional compounds include phosphines, especiallytrimethylphosphine, triethylphosphine, triphenylphosphine andbis(1,2-dimethylphosphino)ethane, P(OR)₃; ethers, especiallytetrahydrofuran; amines, especially pyridine, bipyridine,tetramethylethylenediamine (TMEDA), and triethylamine; olefins, andconjugated dienes having from 4 to 40 carbon atoms. Complexes includingthe latter X′ groups include those wherein the metal is in the +2 formaloxidation state.

All references to the Periodic Table of the Elements herein shall referto the Periodic Table of the Elements, published and copyrighted by CRCPress, Inc., 1989. Also, any references to a Group or Groups shall be tothe Group or Groups as reflected in this Periodic Table of the Elementsusing the IUPAC system for numbering groups.

Zwitterionic complexes result from activation of a Group 4 metal dienecomplex, that is, complexes in the form of a metallocyclopentene whereinthe metal is in the +4 formal oxidation state, by the use of a Lewisacid activating cocatalyst, especially tris(perfluoroaryl)boranecompounds. These zwitterionic complexes are believed to correspond tothe formula:

wherein:

M* is a Group 4 metal in the +4 formal oxidation state;

L and Z are as previously defined;

X** is the divalent remnant of the conjugated diene, X′, formed by ringopening at one of the carbon to metal bonds of a metallocyclopentene;and

A³¹ is the moiety derived from the activating cocatalyst.

As used herein, the recitation “noncoordinating, compatible anion” meansan anion which either does not coordinate to component a 1) or which isonly weakly coordinated therewith remaining sufficiently labile to bedisplayed by a neutral Lewis base. A non-coordinating, compatible anionspecifically refers to a compatible anion which when functioning as acharge balancing anion in the catalyst system of this invention, doesnot transfer an anionic substituent or fragment thereof to said cationthereby forming a neutral four coordinate metallocene and a neutralmetal byproduct. “Compatible anions” are anions which are not degradedto neutrality when the initially formed complex decomposes and arenoninterfering with desired subsequent polymerizations.

Preferred metal complexes a1) used according to the present inventionare complexes corresponding to the formula:

wherein:

R independently each occurrence is a group selected from hydrogen,hydrocarbyl, halohydrocarbyl, silyl, germyl and mixtures thereof, saidgroup containing up to 20 nonhydrogen atoms;

M is titanium, zirconium or hafnium;

Z is a divalent moiety comprising boron, or a member of Group 14 of thePeriodic Table of the Elements, and also comprising nitrogen,phosphorus, sulfur or oxygen, said moiety having up to 60 nonhydrogenatoms;

X and X′ are as previously defined;

p is 0, 1 or 2; and

q is 0 or 1 ;

with the proviso that;

when p is 2, q is 0, M is in the +4 formal oxidation state, and X is ananionic ligand selected from the group consisting of halide,hydrocarbyl, hydrocarbyloxy, di(hydrocarbyl)arnido,di(hydrocarbyl)phosphido, hydrocarbylsulfido, and silyl groups, as wellas halo-, di(hydrocarbyl)amino-, hydrocarbyloxy- anddi(hydrocarbyl)phoshino-substituted derivatives thereof, said X grouphaving up to 20 nonhydrogen atoms,

when p is 1, q is 0, M is in the +3 formal oxidation state, and X is astabilizing anionic ligand group selected from the group consisting ofallyl, 2-(N,N-dimethylaminomethyl)phenyl, and2-(N,N-dimethyl)aminobenzyl, or M is in the +4 formal oxidation state,and X is a divalent derivative of a conjugated diene, M and X togetherforming a metallocyclopentene group, and

when p is 0, q is 1, M is in the +2 formal oxidation state, and X′ is aneutral, conjugated or nonconjugated diene, optionally substituted withone or more hydrocarbyl groups, said X′ having up to 40 carbon atoms andforming a π-complex with M.

More preferred coordination complexes a1) used according to the presentinvention are complexes corresponding to the formula:

wherein

R independently each occurrence is hydrogen or C₁₋₆ alkyl;

M is titanium; Y is —O—, —S—, —NR*—, —PR*—;

Z* is SiR*₂, CR*₂, SiR*₂SiR*₂, CR*₂CR*₂, CR*═CR*, CR*₂SiR*₂, or GeR*₂;

R* each occurrence is independently hydrogen, or a member selected fromhydrocarbyl, hydrocarbyloxy, silyl, halogenated alkyl, halogenated aryl,and combinations thereof, and R* having up to 20 nonhydrogen atoms, andoptionally, two R* groups from Z (when R* is not hydrogen), or an R*group from Z and an R* group from Y form a ring system;

p is 0, 1 or 2;

q is 0 or 1;

with the proviso that:

when p is 2, q is 0, M is in the +4 formal oxidation state, and X isindependently each occurrence methyl or benzyl,

when p is 1, q is 0, M is in the +3 formal oxidation state, and X is 2(N,N-dimethyl)aminobenzyl); or M is in the +4 formal oxidation state andX is 1,4-butadienyl, and

when p is 0, q is 1, M is in the +2 formal oxidation state, and X′ is1,4-dipenyl-1,3-butadiene or 1,3-pentadiene, The latter diene isillustrative of unsymetrical diene groups that result in production ofmetal complexes that are actually mixtures of the respective geometricalisomers.

Exemplary constrained geometry metal complexes are described inInternational Patent Publication WO 97/26297, particularly at pages25-28, which are incorporated herein by reference.

The complexes can be prepared by use of well known synthetic techniques.A preferred process for preparing the metal complexes is is disclosed inU.S. Pat. No. 5,491,246, the teachings of which are hereby incorporatedby reference. The reactions are conducted in a suitable noninterferingsolvent at a temperature from −100 to 300° C., preferably from −78 to100° C., most preferably from 0 to 50° C. A reducing agent may be usedto cause the metal M to be reduced from a higher to a lower oxidationstate. Examples of suitable reducing agents are alkali metals, alkalineearth metals, aluminum and zinc, alloys of alkali metals or alkalineearch metals such as sodium/mercury amalgam and sodium/potassium alloy,sodium naphthalenide, potassium graphite, lithium alkyls, lithium orpotassium alkadienyls, and Grignard reagents.

Suitable reaction media for the formation of the complexes includealiphatic and aromatic hydrocarbons, ethers, and cyclic ethers,particularly branched-chain hydrocarbons such as isobutane, butane,pentane, hexane, heptane, octane, and mixtures thereof; cyclic andalicyclic hydrocarbons such as cyclohexane, cycloheptane,methylcyclohexane, methylcycloheptane, and mixtures thereof; aromaticand hydrocarbyl-substituted aromatic compounds such as benzene, toluene,and xylene, C₁₋₄ dialkyl ethers, C₁₋₄ dialkyl ether derivatives of(poly)alkylene glycols, and tetrahydrofuran. Mixtures of the foregoingare also suitable.

Suitable activating cocatalysts useful in combination with component a1)are those compounds capable of abstraction of an X substituent from a1)to form an inert, noninterfering counter ion, or that form azwitterionic derivative of a1). Suitable activating cocatalysts for useherein include perfluorinated tri(aryl)boron compounds, and mostespecially tris(pentafluorophenyl)borane; nonpolymeric, compatible,noncoordinating, ion forming compounds (including the use of suchcompounds under oxidizing conditions), especially the use of ammonium-,phosphonium-, oxonium-, carbonium-, silylium- or sulfonium-salts ofcompatible, noncoordinating anions, and ferritenium salts of compatible,noncoordinating anions. Suitable activating techniques include the useof bulk electrolysis (explained in more detail hereinafter). Acombination of the foregoing activating cocatalysts and techniques maybe employed as well. The foregoing activating cocatalysts and activatingtechniques have been previously taught with respect to different metalcomplexes in the following references: U.S. Pat. No. 5,153,157, U.S.Pat. No. 5,064,802, U.S. Pat. No. 5,278,119, U.S. Pat. No. 5,407,884,U.S. Pat. No. 5,483,014, U.S. Pat. No. 5,321,106, and EP-A-520,732, theteachings of which are hereby incorporated by reference.

More particularly, suitable ion forming compounds useful as cocatalystscomprise a cation which is a Bronsted acid capable of donating a proton,and a compatible, noncoordinating anion, A⁻.

Preferred anions are those containing a single coordination complexcomprising a charge-bearing metal or metalloid core which anion iscapable of balancing the charge of the active catalyst species (themetal cation) which may be formed when the two components are combined.Also, said anion should be sufficiently labile to be displaced byolefinic, diolefinic and acetylenically unsaturated compounds or otherneutral Lewis bases such as ethers or nitrites. Suitable metals include,but are not limited to, aluminum, gold and platinum. Suitable metalloidsinclude, but are not limited to, boron, phosphorus, and silicon.Compounds containing anions which comprise coordination complexescontaining a single metal or metalloid atom are, of course, well knownarid many, particularly such compounds containing a single boron atom inthe anion portion, are available commercially. Preferably suchcocatalysts may be represented by the following general formula:

(L*−H)_(d) ⁺(A)^(d−)

wherein:

L* is a neutral Lewis base;

(L*−H)⁺ is a Bronsted acid;

A^(d−) is a noncoordinating, compatible anion having a charge of d−, and

d is an integer from 1-3.

More preferably A^(d−) corresponds to the formula: [M′Q₄]⁻;

wherein:

M′ is boron or aluminum in the formal +3 formal oxidation state; and

Q independently each occurrence is selected from hydride, dialkylamido,halide, hydrocarbyl, hydrocarbyloxide, halosubstituted-hydrocarbyl,halosubstitutedhydrocarbyloxy, and halosubstituted silylhydrocarbylradicals (including perhalogenated hydrocarbylperhalogenatedhydrocarbyloxy- and perhalogenated silylhydrocarbyl radicals), said Qhaving up to 20 carbons with the proviso that in not more than oneoccurrence is Q halide.

Examples of suitable hydrocarbyloxide Q groups are disclosed in U.S.Pat. No. 5,296,433, the teachings of which are herein incorporated byreference.

In a more preferred embodiment, d is 1, that is, the counter ion has asingle negative charge and is A⁻. Activating cocatalysts comprisingboron which are particularly useful in the preparation of catalysts ofthis invention may be represented by the following general formula:

(L*−H)⁺(BQ₄)⁻;

wherein:

L* is as previously defined;

B is boron in a formal oxidation state of 3; and

Q is a hydrocarbyl-, hydrocarbyloxy-, fluorinated hydrocarbyl-,fluorinated hydrocarbyloxy-, or fluorinated silylhydrocarbyl-group of upto 20 nonhydrogen atoms, with the proviso that in not more than oneoccasion is Q hydrocarbyl.

Most preferably, each occurrence of Q is a fluorinated aryl group,especially, a pentafluorophenyl group.

Illustrative, but not limiting, examples of boron compounds which may beused as an activating cocatalyst in the preparation of the improvedcatalysts of this invention are trisubstituted ammonium salts such as:

trimethylammonium tetrakis(pentafluorophenyl) borate, triethylammonium

tetrakis(pentafluorophenyl) borate, tripropylammonium

tetrakis(pentafluorophenyl) borate, tri(n-butyl)ammonium

tetrakis(pentafluorophenyl) borate, tri(sec-butyl)ammonium

tetrakis(pentafluorophenyl) borate, N,N-dimethylanilinium

tetrakis(pentafluorophenyl) borate, N,N-dimethylanilinium

n-butyltris(pentafluorophenyl) borate, N,N-dimethylanilinium

benzyltris(pentafluorophenyl)borate, N,N-dimethylanilinium

tetrakis(4-(t-butyldimethylsilyl)-2,3,5,6-tetrafluorophenyl) borate,

N,N-dimethylaniliniumtetrakis(4-(triisopropysilyl)-2,3,5,6-tetrafluorophenyl) borate,N,N-dimethylanilinium pentafluorophenoxytris(pentafluorphenyl) borate,

N,N-diethylanilinium tetrakis(pentafluorphenyl) borate,

N,N-dimethyl-2,4,6-trimethylanilinium tetrakis(pentafluorophenyl)borate,

trimethylammonium tetrakis (2,3,4,6-tetrafluorophenyl)borate,

triethylammonium tetrakis (2,3,4,6-tetrafluorophenyl) borate,

tripropylammonium tetrakis (2,3,4,6-tetrafluorophcnyl) borate,

tri(n-butyl)ammonium tetrakis (2,3,4,6-tetrafluorophenyl) borate,

dimethyl(t-butyl)ammonium tetrakis (2,3,4,6-tetrafluorophenyl) borate,

N,N-dimethylanilinium tetrakis (2,3,4,6-tetrafluorophenyl) borate,

N,N-diethylanilinium tetrakis (2,3,4,6-tetrafluorophenyl) borate, and

N,N-dimenhyl-2,4,6-trimethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)

borate; disubstituted ammonium salts such as: di-(i-propyl) ammonium

tetrakis(pentafluorophenyl) borate, and dicyclohexylammonium

tetrakis(pentafluorophenyl) borate; trisubstituted phosphonium saltssuch as: triphenylphosphonium tetrakis(pentafluorophenyl) borate,

tri(o-tolyl)phosphonium tetrakis(pentafluorophenyl)borate, and

tri(2,6-dimethylphenyl)phosphonium tetrakis(pentafluorophenyl) borate;

disubstituted oxonium salts such as: diphenyloxoniumtetrakis(pentafluorophenyl) borate,

di(o-tolyl)oxonium tetrakis(pentafluororphenyl) borate, and

di(2,6-dimethylphenyl oxonium tetrakis (pentafluorophenyl) borate;

disubstituted sulfonium salts such as: diphenylsulfoniumtetrakis(pentafluorophenyl) borate,

di(o-tolyl)sulfoniumtetrakis(pentafluorophenyl) borate, and

bis(2,6-dimethylphenyl)sulfonium tetrakis(pentafluorophenyl) borate

Preferred (L*−H)⁺ cations are N,N-dimethylanilinium andtributylammonium.

Another suitable ion forming, activating cocatalyst comprises a salt ofa cationic oxidizing agent and a noncoordinating, compatible anionrepresented by the formula:

(Ox^(e+))^(d)(A^(d−))^(e).

wherein:

Ox^(e+) is a cationic oxidizing agent having a charge of e+;

e is an integer from 1 to 3; and

A^(d−) and d are as previously defined.

Examples of cationic oxidizing agents include: ferrocenium,hydrocarbyl-substituted ferrocenium, Ag⁺ or Pb⁺². Preferred embodimentsof A^(d−) are those anions previously defined with respect to theBronsted acid containing activating cocatalysts, especiallytetrakis(pentafluorophenyl)borate.

Another suitable ion forming, activating cocatalyst comprises a compoundwhich is a salt of a carbenium ion and a noncoordinating, compatibleanion represented by the formula:

©⁺A⁻

wherein:

©⁺ is a C₁₋₂₀ carbenium ion; and

A⁻ is as previously defined.

A preferred carbenium ion is the trityl cation, i.e. triphenylmethylium.

A further suitable ion forming, activating cocatalyst comprises acompound which is a salt of a silylium ion and a noncoordinating,compatible anion represented by the formula:

R′″₃Si*A⁻

wherein:

R′″ is C₁₋₁₀ hydrocarbyl, and A⁻ is as previously defined.

Preferred silylium salt activating cocatalysts are trimethylsilyliumtetrakispentafluorophenylborate, triethylsilyliumtetrakispentafluorophenylborate and ether substituted adducts thereof.

Silylium salts have been previously generically disclosed in J. ChemSoc. Chem. Comm. 1993, 383-384, as well as Lambert, J. B., et al,Organometallics, 1994, 13, 2430-2443. The use of the above silyliumsalts as activating cocatalysts for addition polymerization catalysts isdisclosed in U.S. Pat. No. 5,625,087, which is incorporated herein byreference.

Certain complexes of alcohols, mercaptans, silanols, and oximes withtris(pentafluorophenyl)borane are also effective catalyst activators andmay be used according to the present invention. Such cocatalysts aredisclosed in U.S. Pat. No. 5,296,433, the teachings of which are hereinincorporated by reference.

The technique of bulk electrolysis involves the electrochemicaloxidation of the metal complex under electrolysis conditions in thepresence of a supporting electrolyte comprising a noncoordinating, inertanion. In the technique, solvents, supporting electrolytes andelectrolytic potentials for the electrolysis are used such thatelectrolysis byproducts that would render the metal complexcatalytically inactive are not substantially formed during the reaction.More particularly, suitable solvents are materials that are (i) liquidsunder the conditions of the electrolysis (generally temperatures from 0to 100° C.), (ii) capable of dissolving the supporting electrolyte, and(iii) inert. “Inert solvents” are those that are not reduced or oxidizedunder the reaction conditions employed for the electrolysis. It isgenerally possible in view of the desired electrolysis reaction tochoose a solvent and a supporting electrolyte that are unaffected by theelectrical potential used for the desired electrolysis. Preferredsolvents include diduorobenzene (all isomers), dimethoxyetllane (DME),and mixtures thereof.

The electrolysis may be conducted in a standard electrolytic cellcontaining an anode and cathode (also referred to as the workingelectrode auld counterelectrode respectively). Suitable materials ofconstruction for the cell are glass, plastic, ceramic and glass-coatedmetal. The electrodes are prepared from inert conductive materials, bywhich are meant conductive materials that are unaffected by the reactionmixture or reaction conditions. Platinum or palladium are preferredinert conductive materials. Normally an ion permeable membrane such as afine glass grit separates the cell into separate compartments, theworking electrode compartment and counterelectrode compartment. Theworking electrode is immersed in a reaction medium comprising the metalcomplex to be activated, solvent, supporting electrolyte, and any othermaterials desired for moderating the electrolysis or stabilizing theresulting complex. The counterelectrode is immersed in a mixture of thesolvent and supporting electrolyte. The desired voltage may bedetermined by theoretical calculations or experimentally by sweeping thecell using a reference electrode such as silver electrode immersed inthe cell electrolyte. The background cell current, the current draw inthe absence of the desired electrolysis, is also determined. Theelectrolysis is completed when the current drops from the desired levelto the background level. In this manner, complete conversion of theinitial metal complex can be easily detected.

Suitable supporting electrolytes are salts comprising a cation and acompatible, noncoordinating anion, A⁻. Preferred supporting electrolytesare salts corresponding to the formula G⁺A⁻ wherein G⁺ is a cation whichis nonreactive towards the starting and resulting complex, and A⁻ is aspreviously defined.

Examples of cations, G⁺, include tetrahydrocarbyl substituted ammoniumor phosphonium cations having up to 40 nonhydrogen atoms. Preferredcations are the tetra(n-butyl)ammonium and tetra(ethyl)ammonium cations.

During activation of the complexes of the present invention by bulkelectrolysis, the cation of the supporting electrolyte passes to thecounterelectrode and A⁻ migrates to the working electrode to become theanion of the resulting oxidized product. Either the solvent or thecation of the supporting electrolyte is reduced at the counterelectrodein equal molar quantity with the amount of oxidized metal complex formedat the working electrode. Preferred supporting electrolytes aretetrahydrocarbylammonium salts of tetrakis(perfluoroaryl) borates havingfrom 1 to 10 carbons in each hydrocarbyl or perfluoroaryl group,especially tetra(n-butylammonium)tetrakis{pentafiuorophenyl) borate.

A further recently discovered electrochemical technique for generationof activating cocatalysts is the electrolysis of a disilane compound inthe presence of a source of a noncoordinating compatible anion. All ofthe foregoing techniques are more fully disclosed and claimed inpublished international patent application WO 95/00683. In as much asthe activation technique ultimately produces a cationic metal complex,the amount of such resulting complex formed during the process can bereadily determined by measuring the quantity of energy used to form theactivated complex in the process.

Alumoxanes, especially methylalumoxane or triisobutylaluminum modifiedmethylalumoxane are also suitable activators and may be used foractivating the metal complexes.

A most preferred activating cocatalyst is trispentafluorophenylborane.

The molar ratio of metal complex: activating cocatalyst employedpreferably ranges from 1:1000 to 2:1, more preferably from 1:5 to 1.5:1,most preferably from 1:2 to 1:1.

In general, the polymerization may be accomplished at conditions wellknown in the prior art for Ziegler-Natta or Kaminsky Sinn typepolymerization reactions, that is, temperatures from 0 to 250° C. andpressures from atmospheric to 1000 atmospheres (100 MPa). Suspension,solution, slurry, gas phase or other polymerization process conditionsmay be employed if desired, however, solution polymerization processconditions, especially continuous solution polymerization processconditions, are preferred. A support may be employed but preferably thecatalysts are used in a homogeneous manner, ie dissolved in the solvent.Of course, the active catalyst system can form in sitti if the catalystand its cocatalyst components are added directly to the polymerizationprocess and a suitable solvent or diluent (e.g. hexane, iso-octane,etc.) including condensed monomer, are also used. Preferably the activecatalyst is formed separately in a suitable solvent, e.g. in a slipstream, prior to adding it to the polymerization mixture.

As previously mentioned, the above catalyst system is particularlyuseful in the preparation of elastomeric polymers in high yield andproductivity. The process employed may be either a solution or slurryprocess both of which are previously known in the art. Kaminsky, J.Poly. Sci., Vol. 23, pp. 2151-64 (1985) reports the use of a solublebis(cyclopentadienyl) zirconium dimethyl-alumoxane catalyst system forsolution polymerization of EPDM elastomers. U.S. Pat. No. 5,229,478discloses a slurry polymerization process utilizing similarbis(cyclopentadienyl) zirconium based catalyst systems. In general, itis desirable to produce the elastomers for use in the present inventionunder conditions of increased reactivity of the diene monomer component.

Advantageously, a single site catalyst, e.g. a monocyclopentadienyl or-indenyl metallocene, is chosen that allows for increased dienereactivity which results in the preparation of ethylene/α-olefin/dienepolymers in high yield. For example, the monocyclopentadienyl andindenyl metallocene catalysts, described previously, perform well inthis respect. Additionally, these catalyst systems achieve theeconomical production of fast curing ethylene/α-olefin/diene polymerswith diene contents of up to 20 weight percent.

Preferred ethylene/α-olefin/diene polymer products are made with acatalyst that is free of aluminum (the presence of which has adetrimental effect on certain of the product physical properties, e.g.color). Moreover, due to the high efficiency of these aluminum-freecatalysts, less is required and since less is required, less catalystresidue is present in the final product. In fact so little catalystresidue is present in the final product that the process of theseembodiments does not require a catalyst residue removal or treatmentstep as is required in conventional processes. Theethylene/(α-olefin/diene polymer products made using such catalysts arealso substantially free of color bodies.

Another aspect of the present invention is a process for fabricating thepolymer mixture of the invention into the form of an article. Fabricatedarticles may be made from ethylene/α-olefin/diene polymer modifiedaccording to this invention using any conventional EPDM processingtechnique. The process can include a lamination and coextrusiontechnique or combinations thereof, or using the polymer mixture alone,and includes a blown film, cast film, extrusion coating, injectionmolding, blow molding, compression molding, rotomolding, or injectionblow molding operation or combinations thereof, calendering, sheetextrusion, profile extrusion to make a film, a molded article or anarticle comprising an ethylene/α-olefin/diene polymer film layer orcoating and extrusion, injection molding, etc., of the modifiedelastomer with a blowing agent to make an article comprising foamrubber.

The new polymers described herein are particularly useful for wire andcable coating operations, as well as in sheet extrusion for vacuumforming operations.

Modification of the selected polymer according to this inventioninvolves partially crosslinking the selected ethylene/α-olefin/dienepolymer to make a modified ethylene/α-olefin/diene polymer satisfyingthe following equations:$W \leq \left( \frac{{MS}_{2} - {MS}_{1}}{{MS}_{1}} \right)$

wherein MS₁, MS₂, and W are measured as defined above. The Mooneyviscosity for the elastomers after modification according to thisinvention preferably ranges from a minimum of about 10, more preferablyat least about 15, even more preferably at least about 20, and even morepreferably about 30, up to a maximum viscosity of about 100, morepreferably up to about 80 and even more preferably up to about 70.Preferably, MS₁ is preferably not greater than 20, MS₂ is preferably atleast 80, and W is preferably about 0.5, more preferably about 0.7, morepreferably about 0.8, even more preferably about 5.0, even morepreferably about 7.0 and even more preferably about 8.0.

The % gel of the modified polymer is preferably less than or equal to60%, more preferably less than 30%, more preferably less than 20%., evenmore preferably less than 10% and even more preferably less than 5%. Themodified polymer preferably has a percent gel that is preferably notmore than about 20 percent greater, more preferably not more than about10 percent greater, than the percent gel of the unmodified polymerselected in step (A).

The rheology of the above polymers is preferably modified to satisfy theequation:${MS}_{2} \geq {\left( {\frac{MV}{X} + \frac{\% \quad {gel}}{Y}} \right)Z}$

in which X is 50, preferably 45, Y is 20, more preferably 10 and evenmore preferably 5, and Z is 40, more preferably 50, and even morepreferably 55, and MS₂, MV and % gel, including their preferred ranges,are as defined above.

Crosslinking agents include peroxide compounds and other knownheat-activated curing agents, such as azo compounds, and electron beam,gamma-ray and other known radiation cure systems. If the crosslinkingagent is a heat-activated substance, e.g. a peroxide, etc., then thisagent is melt processed with the ethylene/α-olefin/diene polymer tomodify the same according to this invention. The various crosslinkingagents can be used alone or in combination with one another. Excess orresidual peroxide may be available for initiating crosslinking alongwith another crosslinking agent, electron beam, etc., to furthercrosslink the ethylene polymer after production of a crosslinked moldedarticle having greater than 30 wt %, preferably at least 60 wt %, evenmore preferably at least 70 wt %, gel up to 100 wt % gel.

Suitable heat-activated crosslinking agents include free radicalinitiators, preferably organic peroxides, more preferably those with onehour half lives at temperatures greater than 120 C. The free radicalinitiators can be selected from a variety of known free radicalinitiators such as peroxides (e.g., di-t-butyl peroxide (available fromElf Atochem), VULCUP™ (a series of vulcanizing and polymerization agentscontaining α,α′-bis(t-butylperoxy)-diisopropylbenzene made by Hercules,Inc.), DI-CUP™ (a series of vulcanizing and polymerization agentscontaining dicumyl peroxide made by Hercules, Inc.), LUPERSOL™ 101(2,5-dimethyl-2,5-di(t-butylperoxy)hexene), LUPERSOL™ 130(2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3), LUPERSOL™ 575 (t-amylperoxy-2-ethylhexonate) (all LUPERSOL™ peroxides are commerciallyavailable from Elf Atochem, North America) or TRIGONOX™ (an organicperoxide made by Noury Chemical Company)) or radiation treatment (γ, β,or α, including electron beam irradiation).

In one embodiment, a heat-activated compound, such as aperoxide-containing compound, may be used as the crosslinking agent. Thepolymer is treated with heat-activated crosslinking agent in the amountrequired to cause modification of the melt strength of the polymer inaccordance with the conditions specified above. When the crosslinkingagent is a peroxide compound, the amount of peroxide compound ispreferably in the range from a minimum of at least about 0.01 mmoles,preferably at least about 0.04 mmoles, up to a maximum of about 0.8mmoles, preferably up to about 0.2 mmoles, peroxide radical/kgethylene/α-olefin/diene polymer. The crosslinking agent concentrationrequired to modify a particular polymer depends on the susceptibility ofthe polymer to crosslinking and is influenced by factors such as itspercentage vinyl unsaturation and the amount of chain branching,especially short chain branching.

The formulations are compounded by any convenient method, including dryblending the individual components and subsequently melt mixing or meltprocessing, spraying the heat-activated crosslinking agent onto solidpolymer pellets and subsequently melt mixing or melt processing or bypre-melt mixing in a separate device (e.g., a Banbury mixer, a Haakemixer, a Brabender internal mixer, or a single screw or twin screwextruder). Compounding with a twin screw extruder, such as model ZSK-53made by Werner and Pfleiderer, is preferred, but other extruderconfigurations may be used such as those disclosed in U.S. Pat. No.5,346,963, which is incorporated herein by reference.

When the crosslinking agent is radiation, the absorbed dose of radiationis preferably in the range from about 1 to about 20 gray (Joules ofabsorbed radiation energy/kg of ethylene/α-olefin/diene polymer).Similar to the case with heat-activated crosslinking agents, the dosagerequired to modify a particular polymer depends on the susceptibility ofthe polymer to crosslinking and is generally influenced by the samefactors. The radiation is preferably applied in a wavelength range fromabout 0.01 to about 1×10⁻⁵ nanometers (nm).

The irradiation conditions are preferably adjusted to avoid unwantedside effects. The irradiation intensity is, for example, preferablyadjusted to avoid substantial heating of the polymer, because that mightcause the polymer to react with oxygen in the air and with oxygendissolved in the polymer, which in turn could cause polymer degradation,resulting in reduction of long-term stability and/or an increasedpotential to form gels, unless additional measures are taken to preventcontact with oxygen. Excessive heating would also risk fusing discretepolymer particles or pellets together, making it inconvenient to usewith conventional melt processing equipment. These side effects may beavoided by adjusting the radiation dosage rate and/or conducting theprocess in an inert atmosphere. Adjusting the radiation dosage rate is,from a practical standpoint, preferable. The radiation dosage rate ispreferably less than 20 Mrad/s, more preferably less than 10 Mrad/s, andeven more preferably less than 7 Mrads/s.

The crosslinking agent treatment may be carried out online. Onlinecrosslinking agent treatment is carried out on the polymer as thepolymer is produced, preferably immediately after polymerization anddevolatilization and prior to first solidification of the polymer(typically by pelletization). When the crosslinking agent is aheat-activated compound, the compound may be added with a solvent or asa concentrate in a masterbatch.

Modification according to this invention may also be carried outoffline. Offline modification may be carried out by treating anunmodified polymer with crosslinking agent after it has been solidified(typically as pellets or granules). When the crosslinking agent isradiating energy, the polymer may be treated by exposing the polymer,preferably as a solid, to the radiating energy under conditions whichallow for control of the amount of energy absorbed by the polymer. Whenthe crosslinking agent is a heat-activated compound as described above,it is either admixed with or coated on the polymer pellets or granulesand then the polymer pellets or granules are melt processed or it isadded to the polymer, directly or preferably in the form of aconcentrate or masterbatch, during melt processing such as through oneof the ports for adding components to the melt often provided on meltprocessing equipment.

A rheology-modified polymer according to this invention may be combinedwith one or more additional polymers to form polymer mixtures. Theadditional polymers may be rheology-modified or unmodified. They may beselected from any of the modified polymers and from the unmodifiedpolymers described above that serve as starting materials formodification according to this invention. The additional polymers mayalso be heterogeneously branched polymers such as low densitypolyethylene (LDPE), linear low density polyethylene polymers (LLDPE),substantially linear ethylene polymers (SLEP), and/or high densityethylene polymers (HDPE). Any of the aforementioned additional polymersmay be grafted or copolymerized with various functional groups.

The polymer mixtures of the present invention may be prepared byphysical blending of those polymers in an appropriate mixer and/orextruder, by combining the flow of two or more reactors used to makethose polymers connected in series or in parallel, and/or by in-reactorblending using two or more catalysts in a single reactor or combinationsof multiple catalysts and multiple reactors. The general principle ofmaking polymer blends by in-reactor blending using two or more catalystsin a single reactor or combinations of multiple catalysts and multiplereactors is described in WO 93/13143; WO 94/01052; EP-A-619827; and U.S.Pat. No. 3,914,342, each of which are incorporated herein by reference.The polymer mixtures can be prepared by selecting appropriate catalystand process conditions with a view to the final compositioncharacteristics and conducting the rheology modification step eitheronline as the polymers are blended or offline after such blending step.

The present invention also encompasses intermediates for making modifiedpolymers according to this invention, which may be melt processed intothe finished article alone or in combination with the other polymersdescribed above. Such intermediates include pellets and granulescomprising the selected polymer crosslinked with radiation orheat-activated compound as described. The intermediates may also bepellets or granules comprising the selected polymer that have beensprayed, coated in some other way, or admixed with unreactedheat-artivated crosslinking agent, such as a peroxide compound or an azocompound. The heat-activated compound may be applied neat, with anadjuvant or with a substance that retards the reactivity of theheat-activated compound at temperatures below the intended meltprocessing temperature. The pellets or granules treated with theheat-activated compound may be further treated to seal theheat-activated compound onto the surface of the pellets or granules, ifnecessary.

Modification according to this invention may be carried out usingpolymer that contains little or no secondary antioxidant. This may bepreferred in cases in which the polymer will undergo further processingin which the manufacturer customizes the polymer with its own additivepackage which includes one or more antioxidants. This may in someinstances also be preferred from a cost and polymer color standpoint,since some antioxidants may react with the crosslinking agent, using upsome of the antioxidant intended to protect the polymer againstoxidation and possibly forming colored byproducts.

This invention also encompasses the products made by all the foregoingprocesses.

This invention is further described by the examples below. Thoseexamples are provided for illustration only and are not to be construedas limiting the scope of the invention described more fully herein.

EXAMPLES Process Description

Rheoloqy Modification

Examples 1-4 are viscosity modified on Haake Rheocord 40 torquerheometer drive unit and Rheomix 3000E mixer (available from HaakeBuchler Instruments) equipped with roller style blades.

Examples 5, 6 and 7 are viscosity modified on a Haake Rheocord 40 torquerheometer drive unit fitted with a Rheomix 202 ¾ inch single screwextruder.

Examples 8, 9 and 10 are viscosity modified on a 1.5 inch diameterKillion single screw extruder.

Base Resins

TABLE I Characteristics of Base Resins EPDM Base Resin Characteristic 12 3 4 5 6 7 8 9 Melt Index .41 4.8 19.2 0.5 0.6 1.1 — — — (I₂ at 190 C)Melt Index 7.3 6.1 6.0 7.0 — — — — — Ratio (I₁₀/ I₂ at 190 C) Mooney 357 2 35 25 18 18 30 41 Viscosity (ML 1 + 4 at 125 C) Wt. % Ethyl- 72 7473 51 70 72 72 71 55 ene Monomer Wt % Propyl- 23 21 22 44 25 23 23 23 41ene Monomer Wt % ENB 5 5 5 5 5 5 5 5 5 Monomer Type* SC SC SC A SC SC SCSC A * “SC” means “semi-crystalline” and “A” means “amorphous”

The additive package for EPDM Base Resins 5, 6 and 7 is 1250 ppm calciumstearate, 1000 ppm Irganox 1076 and about 1600 ppm Sandostab PEPQ.

Crosslinking Agents

The peroxide used for examples 1-4 and 6-7 is 2,5 dimethyl-2,4di(t-butyl peroxy)-3-hexyne (available commercially as Lupersol™ 130)

The peroxide used for examples 5 and 8-10 is 2,5 dimethyl-2,4 di(t-butylperoxy)-3-hexane (available commercially as Lupersol™ 101)

Formulation Ingredients

TABLE 2 Key to Formulation Ingredients Chemical Supplier CompositionCalsol 8240 (aka Sun Process Oils ASTM Type 3 Circosol 4240) Untreatednapthenic oil Captax (MTB) R.T. Vanderbilt Co. lnc. 2-mercapto-benzothiazole Carbon Black Cabot Corporation Carbon Black N330 MethylTuads R.T. Vanderbilt Co. Inc. Tetramethylthiuram (TMTD) disulfideStearic Acid C.P. Hail Stearic Acid Sulfur R.E. Carrol Sulfur Zinc OxideZinc Corporation of Zinc Oxide Powder (Kadox 72) America

Method of Preparing Samples

Rheology Modification

Examples 1-4 are prepared by loading the starting elastomer into themixer at 160 degree C. and 30 rpm mixing speed. The loading ram islowered to force the sample into the mixer and the ram is kept downthroughout the run (except during addition of the peroxide) to minimizeexposure to air. After the elastomer is loaded, the ram is raised andthe liquid peroxide is slowly added using a syringe to direct theperoxide onto the fluxing polymer nip (avoiding the metal surfaces whichcan cause volatilization of the peroxide). The weight of peroxide iscalculated from the weight loss of the syringe. After approximately 3minutes, the temperature is increased to 190 C to decompose theperoxide. The run is continued until the torque reaches a plateau for2-5 minutes, indicating completion of the rheology modificationreaction.

Total mixing time is approximately 15-20 minutes. The sample is removedfrom the mixer and cooled, and then granulated using a low speedColortronic granulator.

Examples 5-7 are prepared by imbibing the elastomer with peroxidesolution, extruding at low temperature to ensure mixing/homogenizationand then extruding at high temperature to perform the rheologymodification reaction. Thus, the samples described are produced byplacing 227 grams of EPDM in a gallon HDPE jar which contains ½″stainless steel ball bearings to keep the polymer from agglomerating,adding peroxide along with 15-20 grams of methyl ethyl ketone, and thenroll blending for to 16 hours. The pellets are then dried at conditionsto remove the methyl ethyl ketone but not to devolatilize the peroxide.The imbibed pellets are then extruded at 110 C, granulated, thenextruded again at 200 C.

Examples 8-9 are prepared by imbibing the elastomer with peroxidesolution, extruding at low temperature to ensure mixing and thenextruding at high temperature to perform the rheology modificationreaction. The imbibing process involves placing the pellets inside a 150lb. HDPE drum. One inch stainless steel ball bearings are added to keepthe polymer from agglomerating. The peroxide is then diluted with methylethyl ketone (MEK) and that solution is quickly poured over the pellets(the amount of MEK is typically 3-5 wt.%). The lid is then closed andthe drum tumbled end over end for 4 to 16 hours. The pellets, ballbearings and imbibed pellets are then poured out on a HDPE film for theMEK to evaporate. The first extrusion step (“homogenizing”) isaccomplished by extruding at 295 F while the extruder is run at 25-45rpm. The second step (“reacting”) is accomplished at 410 F at anextruder speed of 25 rpm.

Example 10 is prepared by imbibing the elastomer with peroxide solution,extruding at low temperature to ensure mixing and then extruding at hightemperature to perform the rheology modification reaction according tothe same procedure as used for examples 8 and 9, except that when thepellets, ball bearings and imbibed pellets are poured out on a HDPE filmfor the MEK to evaporate, this material is reground and then dried byblowing chilled air across the pellets on the HDPE film to reducereagglomeration. The product is also chilled before the second extrusionstep to eliminate clumping.

Formulating

The elastomer formulations for Examples 1, 2 and 3 are prepared with aHaake Rheomix 3000 mixer as described above and then roll milled formelt stength testing as described below.

Formulations

Examples 1-3 are formulated according to ASTM D-3568 #2 as follows:

35.21 wt. % resin

0.35 wt. % stearic acid

1.76 wt. % Kadox 72 Zinc Oxide

35.21 wt. % Carbon Black N330

26.41 wt. % Circosol 4240

0.18 wt. % Captax (MTB)

0.35 wt. % Methyl Tuads (TMTD)

0.53 wt. % Sulfur.

Examples 8-10 are formulated according to ASTM 3865 as follows:

41.84 wt. % resin

0.42 wt. % stearic acid

2.09 wt. % Kadox 72 Zinc Oxide

33.47 wt. % Carbon Black

20.92 wt. % Calsol 8240

0.21 wt. % Captax (MTB)

0.42 wt. % Methyl Tuads (TMTD)

0.63 wt. % Sulfur.

Analysis of Products

Melt Index

According to ASTM at 190 degree C.

Mooney

The data is gathered on a Monsanto MV2000E viscometer at 125 degree C.using the large rotor size and reading the viscosity at 5 minutes (ML1+4).

Melt Strength

Melt strength was measured on a Goettfert Rheotens. The Rheotensmeasures the melt strength as well as the tensile force/velocity. Themelt strength is taken as the plateau of the force velocity curve. Whento testing approximately 10 grams of formulated material is placed inthe capillary rheometer at the correct temperature. The extrudate fromthe rheometer is positioned between the two rotating wheels of theRheotens which are placed close together so the extrudate is drawnthrough the wheels. The wheels are accelerated at 2.4 m/s², and theforce is measured as the function of the velocity of the wheels.Eventually, the extrudate breaks and the test is terminated. Conditionsfor testing are 2.1 mm diameter die, 42 mm length, aspect ratio of 20.0,crosshead speed of 25.4 mm/min, shear rate of 33 reciprocal seconds, airgap between the rheometer outlet and the Rheotens is 100 mm and initialwheel velocity is 10 mm/sec. All tests are run at 110 C to avoidvulcanization of the formulation.

Percent Gel

The amount of gel was determined by pressing small samples (2-3 grams)approximately 2 mil films and then performing a xylene extractionaccording to ASTM conditions with the exception that instead of grindingthe polymer to a powder as is done with polyethylene the thin films areused directly (Wiley mill creates too much heat).

Example 1

Results with Base Resin 1 Mooney Percent Melt Viscosity Peroxide GelStrength at 125 C. (wt. %) (wt. %) (cN) 35 0.000 0.2 21.1 43 0.030 1.037.6 43 0.046 1.0 38.6 54 0.063 0.5 85.4 67 0.087 9.8 84.1 88 0.124 19.415.8

Example 2

Results with Base Resin 2 Mooney Percent Melt Viscosity Peroxide GelStrength at 125 C. (wt. %) (wt. %) (cN) 7 0.000 0.3 5.1 22 0.136 0.316.3 37 0.157 2.4 76.5 55 0.197 29.8 111.6 50 0.266 30.2 70.2

Example 3

Results with Base Resin 3 Mooney Percent Melt Viscosity Peroxide GelStrength at 125 C. (wt. %) (wt. %) (cN) 2 0.000 0.3 0 15 0.241 0.9 10.828 0.299 31.0 40.8 31 0.352 29.4 78.5 50 0.550 52.5 66.5

Example 4

Results with Base Resin 4 Percent Mooney Viscosity Peroxide at 125 C.(wt %) 35 0.000 38 0.067 43 0.071 47 0.076 57 0.090 64 0.108 71 0.131

Example 5

Results with Base Resin 6, Run #1 Percent Mooney Viscosity Peroxide at125 C. (wt %) 18.5 0.000 41 0.085 60 0.112 73 0.133

Example 6

Results with Base Resin 6, Run #2 Percent Mooney Viscosity Peroxide at125 C (wt %) 18.5 0.000 30 0.050 30 0.061 38 0.092 42 0.106

Example 7

Results with Base Resin 5 Percent Mooney Viscosity Peroxide at 125 C.(wt %) 25 0.000 46 0.067 58 0.071

Example 8

Results with Base Resin 7 Percent Mooney Viscosity Peroxide Gel at 125C. (wt %) (wt %) 18.5 0.000 — 33.8 0.062 — 42.4 0.101 — 50.9 0.106 0.2850.8 0.110 0.35

Example 9

Results with Base Resin 8 Percent Mooney Viscosity Peroxide Gel at 125C. (wt %) (wt %) 29.6 0.000 — 51.9 0.060 0.00 53.8 0.068 0.47 50.0 0.0800.34 56.5 0.096 — 69.3 0.106 —

Example 10

Results with Base Resin 9 Percent Mooney Viscosity Peroxide at 125 C (wt%) 19 0.000 39.5 0.075 40.0 0.075 40.6 0.076

As can be seen from the foregoing examples, this invention may beapplied to improve the green strength of a wide range ofethylene/(α-olefin/diene polymers selected according to this inventionwhile maintaining good processability. Melt strength data for Examples1-3, especially Examples 1 and 2, show in particular that melt strengthcan be substantially improved according to this invention without eithera substantial increase in viscosity or substantial formation of gel.

Although the invention has been described in considerable detail throughthe preceding specific embodiments, it is to be understood that theseembodiments are for purposes of illustration only. Many variations andmodifications can be made by one skilled in the art without departingfrom spirit and scope of the invention. in the art without departingfrom the spirit and scope of the invention.

What is claimed is:
 1. A process for improving the green strength ofethylene/α-olefin/diene polymers comprising: (A) selecting anethylene/α-olefin/diene polymer having a Mooney ML1+4 viscosity,measured according to ASTM D 1646 at 125 C up to about 80 and a percentgel, measured according to ASTM D2765, Procedure A, up to about 30percent and (B) partially crosslinking the ethylene/α-olefin/dienepolymer selected in step (A) to make a modified ethylene/α-olefin/dienepolymer satisfying the following equations:$W \leq \left( \frac{{MS}_{2} - {MS}_{1}}{{MS}_{1}} \right)$

 wherein MV is the Mooney viscosity of the modified polymer measured asdefined in step (A), MS₁ is the melt strength in centiNewtons of thepolymer selected in step (A) when formulated according to ASTM D3568#2,MS₂ is the melt strength in centiNewtons of the modified polymer alsowhen formulated according to ASTM D3568#2, and W is 0.3.
 2. The processof claim 1 wherein the modified polymer further satisfies the equation:${MS}_{2} \geq {\left( {\frac{MV}{X} + \frac{\% \quad {gel}}{Y}} \right)Z}$

wherein MS₂, MV and % gel are the melt strength, Mooney viscosity andpercent gel of the modified polymer measured as previously defined andvariables X, Y, and Z are 50, 20 and 40, respectively.
 3. The process ofclaim 1 wherein W is 5.0.
 4. The process of claim 1 wherein MS₂≧80. 5.The process of claim 1 wherein the modified polymer has a percent gel nomore than 10 percent greater than the percent gel of the polymerselected in step (A).
 6. The process of claim 1 wherein the α-olefin ispropylene and the diene is 5-ethylidene-2-norbornene.
 7. The process ofclaim 1 wherein the polymer selected in step (A) has a melt index ratio(I₁₀/I₂@190 C) of less than about
 10. 8. The process of claim 1 whereinthe partial crosslinking is carried out by contacting the polymerselected in step (A) with a peroxide crosslinking agent under meltprocessing conditions.
 9. The process of claim 1 wherein the partialcrosslinking is carried out by exposing the polymer selected in step (A)to radiation having a wavelength less than 0.01 nanometers at anintensity sufficient to generate free radicals in the selected polymer.10. The process of claim 2 wherein W is 5.0, MS₂≧80 and the modifiedpolymer has a percent gel no more than 10 percent greater than thepercent gel of the polymer selected in step (A).